The present invention relates to systems and methods for wireless information and data transmission, and in particular, to frequency reuse for such transmissions.
Frequency reuse is a term used to describe the ability to reuse frequencies for information and data transmission repeatedly within a single system. Presently, frequency reuse is made possible through the basic design approach utilized in cellular technology. A xe2x80x9ccellxe2x80x9d is the basic geographic unit of a cellular system and is served with a low-powered radio frequency transmitter/receiver. Frequency reuse is a common system configuration in which certain frequencies are re-used in distinct areas.
Because a cell in a cellular system is designed to use a given radio frequency only within its given geographic boundary, the same frequencies may be re-used in other, distant, cells with little potential for interference. As a general rule, areas where frequencies are reused must exhibit sufficient isolation from each other so as to avoid co-channel interference. Frequency reuse is the feature that allows a cellular system to handle a very large volume of transmissions with a limited number of channels. Advanced Mobile Phone Service (AMPS), also known as the North American analog cellular phone system, is based upon frequency reuse. AMPS and its variants represent the majority of cellular voice systems installed in the world.
Currently however, frequency reuse is limited due to static geographical boundaries imposed by the need for isolation of areas where frequencies are reused in order to avoid co-channel interference. Thus, there is a need for an apparatus and method that expands the potential for frequency reuse beyond the limitations imposed by static geographic boundaries.
The invention provides an Intelligent Dynamic Frequency Reuse (xe2x80x9cIDFRxe2x80x9d) system that provides sufficient isolation, whether by distance, obstruction, or other means, between the reuse areas to ensure minimal or no co-channel interference, permitting multiple transmissions on a single frequency. For example, the system permits frequency reuse in circumstances in which an obstruction between a transmission site operating on a selected frequency and mobile receiver provides enough isolation so as to allow a second transmitter to transmit to the mobile receiver.
In one embodiment, a method of transmitting and receiving radio signals in a cellular telephone system including a plurality of fixed stations and a plurality of mobile cellular phone system users includes the steps of: (a) transmitting a first signal on a selected frequency with a first one of the plurality of fixed stations, the signal being directed to a first one of the plurality of mobile cellular phone users; (b) receiving a second signal for transmission to a second one of the plurality of mobile cellular phone users at a second one of the fixed stations, transmissions from the second fixed station on the selected frequency being capable of interfering with reception by the first one of the plurality of mobile cellular phone users of transmissions from the first fixed station, (c) determining whether transmission of the second signal on the selected frequency from the second fixed location would interfere with reception of the first signal by the first one of the plurality of mobile cellular phone users, and (d) transmitting the second signal from the second one of the fixed stations on the selected frequency when the transmission will not interfere with simultaneous reception of the first signal by the first one of the plurality of mobile cellular phone users. The method may also contain one or more of the following steps: (1) determining the distance of the first and second mobile users from the first and second fixed stations, (2) determining the location of the first and second mobile users, (3) adjusting the power level at which the second transmission is transmitted to a level at which the transmission will not interfere with reception of the first signal by the first mobile user but sufficient to allow the second mobile user to receive the second signal, (4) adjusting the power level at which the first transmission is transmitted to a level at which the transmission will not interfere with reception of the second signal by the second user but sufficient to allow the first user to receive the first signal, and (5) determining whether a physical obstruction would prevent or block transmission of the second signal on the selected frequency from the second fixed location from interfering with reception of the first signal by the first one of the plurality of mobile cellular phone users and/or searching a database to identify at least one physical obstruction that would prevent transmission of the second signal on the selected frequency from the second fixed location from interfering with reception of the first signal by the first one of the plurality of mobile cellular phone users.
The IDFR system provides for economical system growth and/or system expansion. Initially, radio sites are chosen to provide maximum coverage and as the number of subscribers grows, the number of sites is increased. With the implementation of the IDFR system, new transmitter sites are chosen not for coverage, but for increased capacity. The proliferation of the Internet and DSL technology combined with low-cost base stations which can be interconnected via the Internet establishes an extremely attractive and economical system to deploy in a new area, or to expand in an established area.